Survey:
The survey area also contains all four soil types of the Te Rapa Series, with these soils having both a peaty and humic topsoil.
Fine to coarse gravel is also present in most of the Te Rapa soil profiles throughout the subsoil (Bw, Bs, C, C(g), Cg, and Cr horizons), and can be found in different quantities as some profiles have only a small percentage of fine gravel present.
The main criteria that enables the different variants of the Te Rapa Series to be identified separates the soils out by using the depths to and presence of white or light grey colours and sand or gravel in a profile (Refer to Section One Table).
The Te Rapa soils tend to occur as inclusions within the mapped units of their own soils, which can be seen with the Te Rapa silt loam being present within units of the brown subsoil variant and shallow brown variant (auger descriptions 51, 60, 13).
Soil Description:
The main soil type is the Te Rapa humic or peaty silt loam, with the other soils in the Series being variations of this soil.
These variants are: Te Rapa, shallow brown subsoil variant; Te Rapa, brown subsoil variant; Te Rapa, pale subsoil variant.
The areas where the topsoil is peaty (Oh horizon) or humic (Ah horizon) can be seen clearly on the survey map, with the soils with a peaty top being positioned closer to the deeper peat soils (e.g. Kaipaki Peat) and peat swamps, which occur north of the farm.
The Te Rapa soils have different drainage types, as the Te Rapa peaty and humic silt loam's are moderately well drained soils, and the brown and shallow brown subsoil variants are both well drained soils.
Soil Location:
The Te Rapa soils formed on weathered alluvial material of the Hinuera Formation, this material contains silts over sands and gravel's. The amount of sand and gravel that is present in these soils is what determines the drainage of the soils. The soils are found on flat to gently undulating surface and form on low ridges or mounds of alluvial material.
Loamy sand to sandy textures are common among the Te Rapa soils, with these textures usually occurring in the lower subsoil, but in some cases they can be found in the upper subsoil (e.g. auger descriptions 50, 53, and 62). There are also some locations where the Te Rapa peaty and humic silt loam, pale subsoil variant occurs (auger descriptions 5, 36, 57), an imperfectly drained soil, which is reflected in the mottles present in its profile.
Technical Details:
The main colours seen in the described profiles of the Te Rapa Series soils, for both peaty and humic topsoil were 10YR 2/1 and 2/2.
The subsoil colours for the Te Rapa soils have generally the same range of chromas of 2 to 6 and values of 2 to 8, with 10YR being the most common hue present, but 2.5Y, 7.5YR and 5YR colours have been recorded.
The Te Rapa soils have similar mottle abundance's, sizes, and colours. The Te Rapa peaty and humic silt loam's have few to abundant mottles that have sizes from fine to coarse.
These two soils also have mottle colours of the hues 10YR, 5YR, 7.5YR and 2.5Y, with a range in values of 4 to 7, and a range in chromas of 4 to 8.
The brown subsoil variant has few to profuse mottles present that vary from microfine to coarse in size. The colours of the mottles of this variant have hues of 10YR, 5YR, 7.5YR and 2.5Y, and a range in values of 3 to 8 and chromas of 2 to 8.
The shallow brown subsoil variant has few to abundant mottles that have sizes from microfine to coarse. These mottles have colours that range in values of 3 to 8 and chromas of 2 to 8, with the hues 10YR, 7.5YR, 5YR and 2.5Y being present.
The pale subsoil variant has mottles that are few to common in abundance and microfine to fine in size. This soil has mottle colours of the hues 10YR, 7.5YR and 5YR, that have a range in values of 3 to 6 with chromas of 4 and 8 existing in the profiles.